1. Field of the Invention
This invention relates to gas supply apparatus such as a gas cabinet for delivery of hazardous gases in the manufacture of semiconductor materials and devices, equipped with a scrubber unit to prevent back-migration of the hazardous gases into the ambient environment in which the apparatus is disposed.
2. Description of the Related Art
In the manufacture of semiconductor materials and devices, the semiconductor manufacturing facility (xe2x80x9cfabxe2x80x9d) typically desires to reduce the level of exhaust (by lowering its volumetric flow rate) that is used to ventilate process equipment and process gas storage and dispensing enclosures. Such gas cabinet enclosures hold one or more gas supply vessels, e.g., of conventional high pressure gas cylinder type, or of the kind disclosed in U.S. Pat. No. 5,518,528 to Glenn M. Tom, et al. including sorbent in the gas supply vessel sorptively retaining the gas for subsequent dispensing operation.
Applicable regulations and tracer gas protocols require that gas cabinets be vented at a rate such that xe2x80x9cworse casexe2x80x9d releases cannot create unsafe conditions outside of the gas cabinet enclosure. For example, SEMI S15 tracer gas protocols establish a procedure for testing gas cabinets to ensure that during worst case releases, concentrations of hazardous gas outside the gas cabinet do not exceed xc2xc of the TLV for the gas.
Exhaust air requirements thus are imposed to ensure that the ambient environment of the gas cabinet is not contaminated with hazardous gas at concentrations that compromise the health or safety of personnel in the fab. In consequence, the exhaust air system is overdesigned and requires significant capital investment in pumps, blowers, fans, ducting, etc.
It would therefore be a significant advance in the art to provide a system that permits the exhaust air requirement for the gas cabinet to be reduced, without any countervailing adverse effect on the safety or operability of the gas cabinet.
Other gas storage and gas supply systems have corresponding exhaust gas issues. These include gas storage bunkers, valve manifold boxes (VMBs), and other gas storage, use and distribution systems in which an enclosure holds gas supply vessels and/or gas flow circuitry.
The present invention relates to an enclosure assembly including a gas enclosure defining an enclosed interior volume holding gas supply vessel(s) and/or gas flow circuitry therein and equipped with a back-migration scrubber unit.
In one aspect, the invention relates to a gas containment assembly, comprising:
a containment enclosure defining an enclosed interior volume, and including an exhaust inlet and an exhaust outlet for flow of exhaust gas into the enclosed interior volume through the exhaust inlet and flow through the interior volume for discharge from the containment enclosure through the exhaust outlet;
a gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure;
a back-migration scrubber unit overlying and sealed to the exhaust inlet to permit flow of exhaust gas therethrough into the exhaust inlet, said back-migration scrubber unit comprising a mass of sorbent material having sorptive affinity for gas in said gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure, whereby back-flow migration of gas from said gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure is sorptively taken up by the mass of sorbent material and prevented from passing into an ambient environment in which said gas containment assembly is deployed.
In another aspect, the invention relates to a method of supplying gas to a gas-consuming process, comprising the steps of:
providing a gas containment assembly comprising a containment enclosure defining an enclosed interior volume, and including an exhaust inlet and an exhaust outlet for flow of exhaust gas into the enclosed interior volume through the exhaust inlet and flow through the interior volume for discharge from the containment enclosure through the exhaust outlet, with a gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure;
flowing exhaust gas along an exhaust gas flow path including the exhaust inlet, interior volume of the containment enclosure and exhaust outlet;
disposing in the exhaust gas flow path upstream of the exhaust inlet and in closed flow communication therewith a mass of sorbent material having sorptive affinity for gas in said gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure; and
contacting with said mass of sorbent material any back-flow migration of gas from said gas supply vessel and/or gas flow circuitry in the interior volume of the containment enclosure, whereby back-flow migrating gas is sorptively taken up by the mass of sorbent material and prevented from passing into an ambient environment in which said gas containment assembly is deployed.
Other aspects, features and embodiments in the invention will be more fully apparent from the ensuing disclosure and appended claims.